Editing Cam (mechanism) (section)

==History==
Cam mechanisms appeared in China at around 600 BC in the form of a crossbow trigger-mechanism with a cam-shaped swing arm.<ref>{{cite journal|author1= Kuo-Hung Hsiao|author2=Hong-SenYan|year=2014|title=Mechanisms in Ancient Chinese Books with Illustrations|publisher=[[Springer International Publishing]]|pages=70–71}}</ref> However, the trigger mechanism did not rotate around its own axis and traditional Chinese technology generally made little use of continuously rotating cams.<ref>Joseph Needham: Science and Civilisation in China, Volume 4: Physics and Physical Technology, Part II: mechanical Engineering, Cambridge University Press, 1965, p. 84</ref> Nevertheless, later research showed that such cam mechanisms did in fact rotate around its own axis.<ref>{{cite journal|author1= Kuo-Hung Hsiao|year=2013|title=Structural Synthethis of Ancient Chinese Original Crossbow |pages=270}}</ref> Likewise, more recent research indicates that cams were used in water-driven trip hammers by the latter half of the Western Han Dynasty (206 BC – 8 AD) as recorded in the Huan Zi Xin Lun. Complex pestles were also mentioned in later records such as the Jin Zhu Gong Zan and the Tian Gong Kai Wu, amongst many other records of water-driven pestles.<ref>Hsiao(2014) p71.</ref> During the Tang dynasty, the wooden clock within the water-driven astronomical device, the spurs inside a water-driven armillary sphere, the automated alarm within a five-wheeled sand-driven clock, artificial paper figurines within a revolving lantern, all utilized cam mechanisms.<ref>Hsiao(2014) p71.</ref> The Chinese hodometer which utilized a bell and gong mechanism is also a cam, as described in the Song Shi. In the book Nongshu, the vertical wheel of a water-driven wind box is also a cam.<ref>Hsiao(2014) p71.</ref> Out of these examples, the water-driven pestle and the water driven wind box both have two cam mechanisms inside.<ref>Hsiao(2014) p71.</ref> Cams that rotated continuously and functioned as integral machine elements were built into [[Hellenistic civilization|Hellenistic]] water-driven [[Automaton|automata]] from the 3rd century BC.<ref>{{Citation|last=Lewis|first=M. J. T.|title=Millstone and Hammer. The Origins of Water Power|publisher=The University of Hull Press|year=1997|isbn=0-85958-657-X|pages=84–88}}</ref>

The cam and camshaft later appeared in mechanisms by [[Al-Jazari]], who used them in his automata, described in 1206.<ref>{{cite book|author=Georges Ifrah|year=2001|title=The Universal History of Computing: From the Abacus to the Quantum Computer|pages=171|translator=E.F. Harding|publisher=John Wiley & Sons, Inc.|url=http://www.banffcentre.ca/bnmi/programs/archives/2005/refresh/docs/conferences/Gunalan_Nadarajan.pdf|url-status=dead|archive-url=https://web.archive.org/web/20061008113946/http://www.banffcentre.ca/bnmi/programs/archives/2005/refresh/docs/conferences/Gunalan_Nadarajan.pdf|archive-date=October 8, 2006}}</ref> The cam and camshaft appeared in European mechanisms from the 14th century.<ref>{{cite book|author=A. Lehr|year=1981|title=De Geschiedenis van het Astronomisch Kunstuurwerk|pages=227|publisher=Den Haag.|url=http://odur.let.rug.nl/~koster/musicbox/musicbox2.htm|url-status=dead|archive-url=https://web.archive.org/web/20101025175626/http://odur.let.rug.nl/~koster/musicbox/musicbox2.htm|archive-date=October 25, 2010}}</ref> Waldo J Kelleigh of Electrical Apparatus Company patented the adjustable cam<ref>{{cite web |title=Cam Patent |url=https://patents.google.com/patent/US2922318A/en}}</ref> in the United States in 1956 for its use in mechanical engineering and weaponry.